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Chapter 3

Chapter 3. Applications of Data Communications. Interoperability. A three layers model. Applications Layer. Internet & Transport Layer. Connectivity. Networks Layer. Data Communications Applications File & print serving Mail Domain Name Server Telnet File Transfer Protocol

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Chapter 3

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  1. Chapter 3 Applications of Data Communications

  2. Interoperability A three layers model. Applications Layer Internet & Transport Layer Connectivity Networks Layer

  3. Data Communications Applications File & print serving Mail Domain Name Server Telnet File Transfer Protocol World Wide Web Multi-media Applications Voice Images Contents

  4. Data Communications Applications File & print serving Mail Domain Name Server Telnet File Transfer Protocol World Wide Web Multi-media Applications Voice Images Contents

  5. File server Applications server Print server m4 File & Print Serving Connectionless disc serving Connection oriented printer serving

  6. Data Communications Applications File & print serving Mail Domain Name Server Telnet File Transfer Protocol World Wide Web Multi-media Applications Voice Images Contents

  7. m4 a@m1 b@m2 c@m4 d@m4 email m4 is a mail server with a mailbox for each registered user. Connection between mail server and users can be temporary (direct or via internet) INTERNET d@m4

  8. m4 b@m2 c@m4 d@m4 a@m1 Email Protocols pop/imap server Mail Transfer Agent (X400) http pop3 imap SMTP User Agent Exchange Outlook Netscape Eudora

  9. Data Communications Applications File & print serving Mail Domain Name Server Telnet File Transfer Protocol World Wide Web Multi-media Applications Voice Images Contents

  10. Addresses composed of meaningful fields Address = hierarchical list of domain names A domain is an organizational and/or geographic entity regrouping lower level domains or hosts. Addresses belonging to a given domain are maintained by the authority of that domain. Example : classical telephone numbers 32 2 629 2905, 32 475 819327 hierarchy jeopardized by number portability! Hierarchical Addresses

  11. Organizational and geographic hierarchy do not necessarily match Address values contain no useful information Example : Internet network ID’s VUB = 134.184 ULB = 164.015 KUL = 134.058 KULAK = 193.190 RUG = 157.193 Using large set of flat addresses user-unfriendly Solution : Assign a flat and an hierarchical address to every user and maintain a database linking both Flat Addresses

  12. Root be edu com org ac vub info tiberghien Internet Domains uk ieee mtv fgov vrt ulb lvhamme tiberghien@info.vub.ac.be

  13. In Each domain, there is at least one DNS Name & DNS Address of all subdomains Name & address of all hosts in the domain DNS address of, at least, root of DNS system Names & DNS addresses of frequently used domains Each host must know the address of one DNS Local DNS is locally maintained Caching greatly improves performance of DNS by keeping the translations of most recently accessed domains and hosts Domain Name Servers

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